What aircraft was involved and where did it happen?

The accident on null involved a aircraft, at DE.

What was the probable cause of the accident?

A massive smoldering fire in the Emergency Power Switch, caused by mechanical and electrical overload, led to cockpit smoke and the loss of essential flight instrumentation.

Electrical Fire Forces Emergency Return to Munich in MD-81

A McDonnell Douglas MD-81 experienced heavy cockpit smoke and electrical failures during a flight from Munich to Zurich, leading to an emergency landing and evacuation.

What happened

On October 16, 1993, a McDonnell Douglas MD-81 operating a scheduled flight from Munich to Zurich experienced a significant electrical malfunction shortly after departure. Approximately ten minutes into the flight, while climbing through FL 180, the flight crew detected an unusual odor followed by the appearance of smoke near the landing light switches.

As the smoke intensified, the crew attempted to identify the source using the "Electrical Smoke in Cockpit" checklist. The smoke was traced to the overhead panel, and the crew decided to return to Munich. During the descent, the crew attempted to manage the electrical load by switching off the right generator. This action caused a near-total failure of the left-side flight instrumentation. Due to the increasing density of the smoke, the crew declared an emergency.

Visibility in the cockpit became extremely degraded, forcing the pilot to rely on verbal airspeed updates from the co-pilot. During the final approach, the pilot could only see the airspeed indicator as a vague shadow. The aircraft landed on runway 08 R, but the pilot was forced to initiate heavy braking because visibility outside the cockpit had also vanished. Following the landing, an emergency evacuation was ordered. During the evacuation, 14 passengers and one crew member sustained minor injuries while exiting via the wings or slides.

The investigation

The BFU investigation involved authorities from the USA and Switzerland, the aircraft owner, the manufacturer, and fire specialists. Investigators analyzed the flight path using radar data, the Cockpit Voice Recorder (CVLT), the Digital Flight Data Recorder (DFDR), and radio communications. The investigation specifically focused on the electrical power supply system and the physical state of the overhead panel components.

Findings

The primary cause of the incident was a severe smoldering fire within the Emergency Power Switch.
The switch failed due to a combination of mechanical and electrical overload.
The fire caused extensive damage to the aircraft's electrical wiring, including the 115V AC bus distribution, relays, and circuit breakers.
During the evacuation, the rear emergency slide failed to deploy because a safety pin required for slide transport had not been removed during assembly.
The intense smoke caused significant contamination of the entire cockpit area.